Superoxide dismutase from Bacillus stearothermophilus. Complete amino acid sequence of a manganese enzyme.

Superoxide dismutase from the thermophilic bacterium Bacillus stearothermophilus is dimeric with a molecular weight of 45 487. It contains one atom manganese(III) per dimeric molecule [Brock, C. J., Harris, J. I., & Sato, S. (1976) J. Mol. Biol. 107, 175-178]. The subunits are identical, and the following primary structure comprising 203 amino acids has been determined: (Formula: see text) The enzyme is identical in 60% of its residues with the Escherichia coli B manganese enzyme [Steinman, H. M. (1978) J. Biol. Chem 253, 8708-8720]. Neither manganese enzyme has significant homology with the Cu/Zn superoxide dismutase from bovine erythrocytes. The secondary structures of the manganese enzymes predicted by McLachlan's method [McLachlan, A. D. (1977) Int.J. Quantum chem. 12, 371-385] indicate that the eight-stranded beta barrel of the Cu/Zn enzyme [Richardson, J.S., Thomas, K. A., Byron, H. R., & Richardson, D. C. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 1349-1353] is absent from the manganese enzymes.